JP6567780B1 - Power converter - Google Patents

Abstract

The power converter of an embodiment has a plurality of cells connected in series with each other. Each cell includes a capacitor, a semiconductor switch, a first power supply circuit, a discharge circuit, a discharge circuit driving unit, and a second power supply circuit. The semiconductor switch performs a switching operation for controlling charging and discharging of the capacitor. The first power supply circuit supplies power for driving the semiconductor switch to the semiconductor switch using the power stored in the capacitor. The discharge circuit discharges the capacitor. The discharge circuit driving unit drives the discharge circuit. The second power supply circuit supplies power for driving the discharge circuit drive unit using the power stored in the capacitor. The lower limit voltage at which the second power supply circuit can operate is lower than the lower limit voltage at which the first power supply circuit can operate.

Description

  Embodiments described herein relate generally to a power conversion apparatus.

  Outputs a voltage that exceeds the breakdown voltage of the switching element by connecting multiple cells in series, such as IGBTs (Insulated Gate Bipolar Transistors) and self-extinguishing switching elements, and unit converters with capacitors that are energy storage elements. Self-excited power converters are known. This type of power converter is called MMC (Modular Multilevel Converter) or the like.

  Here, when an operator approaches the power converter for maintenance or inspection after an accident, it is necessary to discharge the electric charge charged in the capacitor for safety. The power supply circuit for driving the switching element using the cell capacitor as a power source always consumes power even when switching is stopped. In addition, when the power charged in the capacitor is consumed and the voltage output by the capacitor drops below the operating voltage of the power supply circuit, the power supply circuit stops and the charge charged in the cell capacitor can be discharged. Disappear. For this reason, it takes a long time to wait for the self-discharge of the capacitor, and it may be difficult to work quickly.

JP, 2006-208743, A

Makoto Sugawara, Yasufumi Akagi, “PWM Control Method and Operational Verification of Modular Multilevel Converter (MMC)”, IEEJ Paper D (Industrial Applications), Vol. 128, No. 7, pp. 9570965 (2008-7)

  The problem to be solved by the present invention is to provide a power conversion device capable of shortening the time for discharging the electric charge stored in the capacitor included in the cell.

  The power converter of an embodiment has a plurality of cells connected in series with each other. Each cell includes a capacitor, a semiconductor switch, a first power supply circuit, a discharge circuit, a discharge circuit driving unit, and a second power supply circuit. The semiconductor switch performs a switching operation for controlling charging and discharging of the capacitor. The first power supply circuit supplies power for driving the semiconductor switch to the semiconductor switch using the power stored in the capacitor. The discharge circuit discharges the capacitor. The discharge circuit driving unit drives the discharge circuit. The second power supply circuit supplies power for driving the discharge circuit drive unit using the power stored in the capacitor. The lower limit voltage at which the second power supply circuit can operate is lower than the lower limit voltage at which the first power supply circuit can operate.

The block diagram which shows the whole structure of a power converter device. The figure which shows the structure of a cell. The figure which shows the circuit structure of a 2nd electric power feeding circuit and a discharge circuit. The figure which shows the change of the voltage of a capacitor | condenser, and the timing which a discharge circuit operate | moves. The figure which shows the circuit structure of a discharge circuit. The figure which shows the circuit structure of a 2nd electric power feeding circuit and a discharge circuit drive part. The figure which shows the circuit structure of a 2nd electric power feeding circuit. The figure which shows the other example of the circuit structure of a discharge circuit.

  Hereinafter, the power converter of an embodiment is explained with reference to drawings. In the following description, the same reference numerals are given to configurations having the same or similar functions. And the description which overlaps those structures may be abbreviate | omitted.

(First embodiment)
With reference to FIG. 1, the power converter device of 1st Embodiment is demonstrated. FIG. 1 is a configuration diagram showing the overall configuration of the power conversion apparatus 10.

  The power conversion device 10 includes a central control unit 11, a plurality of positive side arms 12, a plurality of negative side arms 13, a transformer TR, and a plurality of buffer reactors L. The power conversion device 10 is an MMC, for example. The power conversion device 10 converts AC power supplied to the power conversion device 10 via the transformer TR into DC power, and converts DC power supplied to the power conversion device 10 to AC power via the transformer TR. To do. In the following explanation, power converter 10 explains the case where AC power supplied to power converter 10 via transformer TR is converted into DC power.

  The central control unit 11 controls a plurality of cells provided in the positive arm 12 and the negative arm 13 respectively. The central control unit 11 and a plurality of cells included in the positive side arm 12 and the negative side arm 13 are connected by, for example, a daisy chain type communication network.

[Overall Configuration of Power Conversion Device 10]
As shown in FIG.
Three-phase AC power is supplied from the AC power source to the transformer TR. The transformer TR includes a set of secondary windings and primary windings for three phases. The three phases are, for example, an alternating R phase, an alternating S phase, and an alternating T phase. The secondary winding side of the transformer TR is supplied with AC R-phase AC power, AC S-phase AC power, and AC T-phase AC power. In the following description and drawings, components for the R phase are denoted by “R”, “S” for the S phase, and “T” for the T phase.

  In the positive arm 12, a plurality of cells 100 are connected in series. In the negative arm 13, a plurality of cells 100 are connected in series. The positive arm 12 includes a positive arm 12R, a positive arm 12S, and a positive arm 12T. The negative arm 13 includes a negative arm 13R, a negative arm 13S, and a negative arm 13T.

  Each arm included in the positive side arm 12 and the negative side arm 13 is configured by connecting N cells 100 (N ≧ 2) in series, and the stepped AC voltage with the cell 100 as a unit converter. Any voltage is output. A stepped AC voltage is output by shifting the timing of the switching operation of a switching element (not shown) included in each cell 100. Details of the configuration of the cell 100 will be described later.

  A plurality of buffer reactors L (buffer reactors L1 to L6 shown in the figure) suppress short-circuit currents that flow between three phases having the positive side arm 12, the buffer reactor L, and the negative side arm 13 as a single phase. To do.

  In each of the positive side arm 12 and the negative side arm 13, the voltage of each cell 100 is added to determine the output voltage. The output voltage of the positive arm 12 becomes a positive (DC) voltage with respect to the neutral point. The positive (DC) voltage generated by the positive arm 12 is output to the terminal TCP. The output voltage of the negative arm 13 becomes a negative (DC) voltage with respect to the neutral point. The negative (DC) voltage generated by the negative arm 13 is output to the terminal TCM. Thereby, the power converter device 10 outputs DC power from between the terminal TCP and the terminal TCM.

  FIG. 2 is a diagram illustrating the configuration of the cell 100. The cell 100 is, for example, a half bridge type chopper cell. Specifically, the cell 100 includes, for example, a cell control unit 101, a discharge circuit 102, a first power supply circuit 103, a voltage detection unit 104, a switching element driving unit 106, a switching element 107a, and a switching element. 107b, a capacitor 105, a second power feeding circuit 108, and a discharge circuit driving unit 109.

  The central control unit 11 outputs a control signal to the cell control unit 101. The control signal includes a converter stop command ES for stopping the power conversion operation of the cell 100. The cell control unit 101 acquires a control signal from the central control unit 11.

  The cell control unit 101 outputs a discharge circuit operation command RS to the second power supply circuit 108. The discharge circuit operation command RS is a command indicating that the power of the capacitor 105 is discharged to the discharge circuit 102. Further, the cell control unit 101 outputs a timing control signal CS for controlling the switching timing of the switching element 107 a and the switching element 107 b included in the switching element driving unit 106 to the switching element driving unit 106.

  The switching element driving unit 106 acquires the timing control signal CS from the cell control unit 101. The switching element driving unit 106 drives the switching element 107a and the switching element 107b based on the timing control signal CS acquired from the cell control unit 101.

  As shown in FIG. 2, the switching element 107 a and the switching element 107 b output a desired DC voltage by being turned on and off by the switching element driving unit 106 using the capacitor 105 as a voltage source.

  Capacitor 105 is connected in parallel to switching elements 107a and 107b connected in series with each other. As the switching elements 107a and 107b, self-extinguishing elements such as GTO, IGBT, and IEGT can be used. Feedback diodes 12a and 12b are connected in antiparallel to the switching elements 107a and 107b. The cell 100 outputs the DC voltage stored in the capacitor 105 when the switching element 107a is turned on and the switching element 107b is turned off, and the switching element 107a is turned off. Zero voltage when is turned on.

  Here, a portion having the same potential as a connection point between the switching element 107a and the switching element 107b is referred to as a terminal CP. A portion having the same potential as the emitter terminal of the switching element 107b and the negative electrode terminal of the capacitor 105 is referred to as a terminal CM. In the cell 100, the terminal CP is connected to the cell 100 on the terminal TCP side of the cell 100, and the terminal CM is connected to the cell 100 on the terminal TCM side of the cell 100. Thereby, the plurality of cells 100 are connected in series. The power conversion device 10 performs power conversion by changing the on / off timing of the switching element 107a and the switching element 107b.

  The first power supply circuit 103 supplies driving power to the switching element 107 a and the switching element 107 b using the electric power stored in the capacitor 105. The first power supply circuit 103 supplies the power supplied from the capacitor 105 to the switching element driving unit 106 and the cell control unit 101.

  The voltage detection unit 104 detects the voltage between the terminals of the capacitor 105. The voltage detection unit 104 outputs the detected value to the cell control unit 101.

  The second power supply circuit 108 supplies power for driving the discharge circuit driving unit 109 using the power stored in the capacitor 105. When the second power supply circuit 108 acquires the discharge circuit operation command RS from the cell control unit 101, the second power supply circuit 108 starts supplying power to the discharge circuit driving unit 109.

  The discharge circuit 102 discharges the capacitor 105. The discharge circuit 102 includes a discharge resistor R1 and a discharge switch SW1. The discharge resistor R1 and the discharge switch SW1 are connected in series between the positive electrode and the negative electrode of the capacitor 105. Note that the discharge switch SW1 is maintained in the cut-off state before the switch control signal SS is supplied from the discharge circuit driver 109.

  The discharge circuit driving unit 109 outputs a switch control signal SS, which is a signal for switching between a conductive state and a cut-off state of the discharge switch SW1 included in the discharge circuit 102, to the discharge switch SW1. The switch control signal SS is a latch signal. That is, the discharge circuit driving unit 109 continues to output the switch control signal SS to the discharge switch SW1 while the voltage Vs is supplied from the second power supply circuit 108. The voltage Vs is an input voltage at which the discharge circuit driving unit 109 can operate, and an input voltage at which the discharge circuit driving unit 109 can drive the discharge circuit 102.

[Circuit Configuration of Discharge Circuit 102]
Here, with reference to FIG. 3, the circuit configuration of the second power feeding circuit 108 and the discharge circuit 102 according to the first embodiment will be described. FIG. 3 is a diagram illustrating a circuit configuration of the second power feeding circuit 108 and the discharge circuit 102.

  In the following description, the voltage stored in the capacitor 105 may be referred to as voltage Vc.

  The discharge switch SW1 of the present embodiment is, for example, an electromagnetic switch. When the discharge switch SW1 becomes conductive, the power stored in the capacitor 105 is consumed by the discharge resistor R1. That is, the discharge circuit 102 discharges the capacitor 105 by turning on the discharge switch SW1.

  The second power supply circuit 108 generates a voltage Vs that drives the discharge circuit driving unit 109. The voltage Vs is a voltage lower than the lower limit value of the input voltage necessary for the operation of the first power supply circuit 103. Specifically, the second power supply circuit 108 includes a power supply switch SW2, a resistor R2 and a resistor R3, a current limiting resistor R4, and a Zener diode D1. For example, the resistance value of the resistor R2 is larger than the resistance value of the resistor R3. Note that the relationship between the resistance value of the resistor R2 and the resistance value of the resistor R3 is not limited to this. The resistance values of the resistors R2 and R3 may be any resistance value as long as the voltage Vc can be lowered to a voltage (for example, about 5 V) that can be input to the discharge circuit driving unit 109. .

  The power supply switch SW2, the resistor R2, and the resistor R3 are connected in series between the positive electrode and the negative electrode of the capacitor 105. The second power supply circuit 108 divides the voltage Vc supplied from the capacitor 105 by the resistor R2 and the resistor R3 to generate the voltage Vs. The voltage Vs is, for example, a voltage of 5 volts.

  The second power supply circuit 108 supplies the generated voltage Vs to the discharge circuit driving unit 109. The discharge circuit driver 109 operates with the voltage Vs supplied from the second power supply circuit 108. The current limiting resistor R4 limits the current supplied from the second power supply circuit 108 to the discharge circuit driving unit 109.

  The power supply switch SW2 is switched between a cut-off state and a conduction state in accordance with a discharge circuit operation command RS supplied from the cell control unit 101. The power supply switch SW2 is maintained in the cut-off state until the discharge circuit operation command RS is supplied. The second power supply circuit 108 does not generate the voltage Vs that is the operating voltage of the discharge circuit driving unit 109 when the power supply switch SW2 is in the cut-off state. The second power supply circuit 108 generates a voltage Vs that is an operating voltage of the discharge circuit driving unit 109 when the power supply switch SW2 is in a conductive state. The Zener diode D1 is a clamping diode having a voltage Vs.

[Discharge timing of capacitor 105]
Here, the discharge timing of the capacitor 105 will be described with reference to FIG. FIG. 4 is a diagram illustrating the change in the voltage Vc of the capacitor 105 and the timing at which the discharge circuit 102 operates.

  From time t0 to time t1, the cell 100 is in an operating state. For this reason, the voltage Vc of the capacitor 105 provided in the cell 100 is the rated voltage of the capacitor.

  It is assumed that an abnormality (for example, an accident) such as a system fault has occurred at time t1. For example, information indicating the occurrence of an accident is input to the central control unit 11 of the power conversion device 10 by a monitoring device that monitors the state of the system. Instead of the configuration in which the information indicating the occurrence of the accident is input by the monitoring device, when the user operating the power conversion device 10 detects this accident, the central control unit 11 is provided with information indicating the occurrence of the accident. An input configuration may be used. Moreover, the structure which a user inputs the converter stop command ES with respect to the central control part 11 with a maintenance may be sufficient.

  The central control unit 11 outputs the converter stop command ES to the plurality of cells 100 included in the power conversion device 10 at time t2 in response to the input of the converter stop command ES.

  The cell control unit 101 that has acquired the converter stop command ES stops the power conversion operation at time t3. Note that the power system of the supply destination may not be able to consume power due to an abnormality such as an accident, and the power supplied from the DC system may be stored in the capacitor 105. For this reason, in the example of FIG. 4, the voltage Vc of the capacitor 105 from time t1 to time t3 changes to a voltage higher than the rated voltage.

  The cell control unit 101, the first power supply circuit 103, and the switching element driving unit 106 included in the cell 100 operate, so that the charge stored in the capacitor 105 is consumed from time t3 to time t4. The voltage Vc of the capacitor 105 is consumed up to the threshold voltage Vth at time t4.

  When the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 becomes lower than the threshold voltage Vth, the cell control unit 101 outputs a discharge circuit operation command RS to the second power supply circuit 108. When the second power supply circuit 108 acquires the discharge circuit operation command RS from the cell control unit 101, the second power supply circuit 108 supplies the voltage Vs to the discharge circuit driving unit 109. Note that the user may detect an accident and perform an operation of causing the cell control unit 101 to output the discharge circuit operation command RS to the second power feeding circuit 108. In addition, the user may perform an operation of causing the cell control unit 101 to output the discharge circuit operation command RS to the second power feeding circuit 108 with maintenance.

  The discharge circuit driving unit 109 supplied with the voltage Vs from the second power supply circuit 108 outputs a switch control signal SS to the discharge switch SW1. The discharge switch SW1 that has acquired the switch control signal SS from the discharge circuit driving unit 109 becomes conductive. As a result, the discharge circuit 102 starts discharging the electric charge of the capacitor 105. That is, the discharge circuit 102 operates when the voltage Vc of the capacitor 105 is lower than the threshold voltage Vth.

  From time t4 to time t5, the cell control unit 101, the switching element driving unit 106, the discharge circuit 102, and the second power feeding circuit 108 consume the charge stored in the capacitor 105. For this reason, the electric charge stored in the capacitor 105 is consumed faster than the cell control unit 101, the first power supply circuit 103, and the switching element driving unit 106 only consume the electric charge stored in the capacitor 105.

  The voltage Vc of the capacitor 105 decreases to the voltage Vss1 at time t5. The voltage Vss1 is a voltage at which the first power supply circuit 103 can operate, and the minimum voltage that can supply drive power to the switching element driving unit 106 is the first power supply circuit 103. Is a voltage that can be output. Note that the voltage at which the cell controller 101 and the switching element driver 106 can operate may be a voltage lower than the voltage Vss1.

  From time t5 to time t6, the second power feeding circuit 108, the discharge circuit driving unit 109, and the discharge circuit 102 discharge the capacitor 105.

  The voltage Vc of the capacitor 105 decreases to the voltage Vss2 at time t6. The voltage Vss2 is a voltage at which the second power supply circuit 108 can operate, and the second power supply circuit 108 outputs a minimum voltage at which the discharge circuit driving unit 109 can be operated. Is a possible voltage. The voltage at which the discharge circuit 102 operates is lower than the lower limit voltage of the operating voltage of the first power supply circuit 103. The voltage Vss2 is desirably set to a voltage lower than a voltage (for example, around 40V) at which work can be performed safely. This voltage Vss2 is a voltage of about 30 volts, for example.

  As described above, the power conversion device 10 of the first embodiment includes the plurality of cells 100 connected in series with each other, and each cell 100 controls the capacitor 105 and the charge / discharge of the capacitor 105. The switching element 107a and the switching element 107b that perform the switching operation and the power stored in the capacitor 105 are used to supply power for driving the switching element 107a and the switching element 107b to the switching element 107a and the switching element 107b. 1, a discharge circuit 102 for discharging the capacitor 105, a discharge circuit drive unit 109 for driving the discharge circuit 102, a discharge circuit drive unit 109, and a discharge circuit 102 using the electric power stored in the capacitor 105. And supply power to drive the second With the feed circuit 108, the operable lower limit voltage second power supply circuit 108 includes a first power supply circuit 103 is lower than the operable lower limit voltage. As a result, the time for discharging the electric charge stored in the capacitor 105 provided in the cell 100 can be shortened.

Thereby, when an abnormality such as an accident occurs, the voltage Vc of the capacitor 105 can be lowered to a safe voltage in a shorter time. That is, the power conversion device 10 can shorten the time for discharging the electric charge stored in the capacitor 105 included in the cell 100.

  In the above description, the cell control unit 101 has described the case where the discharge circuit operation command RS is output to the second power supply circuit 108 based on the converter stop command ES output from the central control unit 11. Not limited to this. When the cell controller 101 determines that the voltage drop rate of the voltage Vc of the capacitor 105 is lower than a predetermined threshold and the capacitor 105 is discharging, the cell control unit 101 outputs the discharge circuit operation command RS You may output to the electric power feeding circuit 108. The voltage drop rate is the ratio (ratio) of the voltage drop amount with respect to time. Thereby, since the power converter device 10 can discharge the electric charge stored in the capacitor 105 even when the converter stop command ES from the central control unit 11 cannot be acquired, the safety can be improved. it can.

  In addition, the cell control unit 101 may output a discharge stop signal, which is a signal for stopping the discharge operation of the discharge circuit 102, to the second power supply circuit 108. Specifically, the second power supply circuit 108 switches the power supply switch SW2 to the cutoff state based on the discharge stop signal acquired from the cell control unit 101. The second power supply circuit 108 in which the power supply switch SW2 is cut off stops supplying the voltage Vs. The power supply switch SW2 is cut off when the supply of the voltage Vs is stopped. As a result, the discharge circuit 102 stops operating.

  As a result, the power conversion device 10 is used, for example, when an abnormality due to an accident is recovered during the discharging operation of the capacitor 105, when the user performs a stop operation for maintenance, or when the power conversion device 10 is stopped due to an accident. The operation of the cell 100 can be resumed early.

  Further, the discharge circuit 102 may stop its operation at a voltage lower than the voltage at which the second power feeding circuit 108 operates. That is, the power conversion device 10 may stop the operation of the discharge circuit 102 even if all the charges of the capacitor 105 are not removed. As described above, the voltage lower than the voltage at which the second power supply circuit 108 operates is a voltage at which work can be performed safely. For this reason, the operator can work safely even if all the charges of the capacitor 105 are not removed, and does not have to wait until all the charges of the capacitor 105 are removed.

In addition, after the power supply operation of the second power supply circuit 108 included in the cell, the cell 100 outputs a signal indicating the operation status of the discharge circuit 102 to the central control unit 11 that controls the plurality of cells 100. May be.
Thereby, the cell 100 can output the value of the voltage Vc of the capacitor 105 to the central control unit 11 even when the capacitor 105 cannot be discharged due to a failure or the like. The central control unit 11 displays the voltage value of the capacitor 105 acquired from the cell 100 on a display unit (not shown). Thereby, the worker who works the power converter 10 can know the value of the voltage Vc of the capacitor 105 for each cell 100, and can improve the safety of the work.

  Further, the cell 100 may output information indicating the time change of the voltage Vc of the capacitor 105 included in the cell to the central control unit 11. In this case, the cell 100 may output the value of the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 to the central control unit 11 via the cell control unit 101. Thereby, the central control part 11 can collect the information which shows the time change of the voltage Vc for every cell 100. FIG.

  Further, the central control unit 11 calculates the timing at which the voltage Vc of the capacitor 105 decreases to a voltage at which the work can be safely performed based on information indicating the time change of the voltage for each cell 100 collected for each cell 100. The central control unit 11 displays a timing at which the calculated voltage Vc of the capacitor 105 decreases to a voltage at which the work can be safely performed and a time change of the voltage Vc for each cell 100 on a display unit (not illustrated). Thereby, the power converter 10 allows the operator to know the discharge state of the capacitor 105.

(Second Embodiment)
Next, a discharge circuit 102a according to the second embodiment will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 5 is a diagram showing a circuit configuration of the discharge circuit 102b.

  As shown in FIG. 5, the discharge circuit 102a is different from the first and second embodiments in that a thyristor TH1 is used for the discharge switch SW1.

  The thyristor TH1 is maintained in the cutoff state before the discharge circuit operation command RS is input from the cell control unit 101 to the second power supply circuit 108. A switch control signal SS is input from the discharge circuit driving unit 109 to the gate of the thyristor TH1. The thyristor TH1 is in a conductive state after the switch control signal SS is once inputted to the gate until no current flows through the thyristor TH1 or a reverse voltage is applied to the thyristor TH1.

(Third embodiment)
Next, with reference to FIG. 6, the 2nd electric power feeding circuit 108c which concerns on 3rd Embodiment is demonstrated. In addition, about the same part as 1st Embodiment, 2nd Embodiment, and 2nd Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 6 is a diagram illustrating a circuit configuration of the second power feeding circuit 108c and the discharge circuit driving unit 109c.

  The second power supply circuit 108c further includes a self-holding switch SW3 and a Zener diode D2. The self-holding switch SW3 is maintained in the cut-off state before the discharge circuit operation command RS is supplied from the cell control unit 101 to the second power feeding circuit 108c. A constant current determined by the sum of the clamp voltage of the Zener diode D2 and the voltage across the resistor R3 (that is, the voltage Vs) and the resistance value of the current limiting resistor R4 flows through the discharge circuit driver 109c.

  The discharge circuit driving unit 109c is, for example, a relay coil. When a constant current flows through the relay coil, the discharge switch SW1 and the self-holding switch SW3 are in a conductive state. The self-holding switch SW3 maintains a state where the voltage Vc is supplied to the second power feeding circuit 108c by being in a conductive state.

(Fourth embodiment)
Next, a cell 100d according to the fourth embodiment will be described with reference to FIG. In addition, about the same part as 1st Embodiment, 2nd Embodiment, 2nd Embodiment, and 3rd Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. FIG. 7 is a diagram illustrating a circuit configuration of the second power feeding circuit 108d.

  The second power supply circuit 108d further includes a signal processing unit 110 and an OR circuit OR in addition to the configuration of the second power supply circuit 108 described above. The OR circuit OR includes two input terminals (hereinafter, a first input terminal and a second input terminal) and one output terminal. A first input terminal of the OR circuit OR is connected to the cell control unit 101. A second input terminal of the OR circuit OR is connected to the signal processing unit 110. The output terminal of the OR circuit OR is connected to a control unit (not shown) that controls opening and closing of the power supply switch SW2.

  As described above, the value of the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 is input to the cell control unit 101. In this case, the cell control unit 101 outputs a discharge circuit operation command RS to the first input terminal of the OR circuit OR. For example, when the cell controller 101 determines that the voltage drop rate of the voltage Vc of the capacitor 105 has dropped below a predetermined threshold and the capacitor 105 is being discharged, the cell controller 101 performs an OR operation on the discharge circuit operation command RS. Output to circuit OR. The discharge circuit operation command RS is, for example, a high level signal.

  The signal processing unit 110 is connected to the input terminal of the discharge circuit driving unit 109. The input terminal of the discharge circuit driving unit 109 is a connection point between the current limiting resistor R4, the cathode of the Zener diode D1, and the discharge circuit driving unit 109. When the power supply switch SW2 is turned on by the discharge circuit operation command RS, the voltage Vs is held at a certain value by the Zener diode D1. The signal processing unit 110 supplies a processing signal SPS to the OR circuit OR when a constant voltage Vs is applied to the input terminal of the discharge circuit driving unit 109. The signal processing unit 110 is an A / D converter that converts the voltage Vs into a digital signal, for example. The processing signal SPS is, for example, a high level signal.

  The OR circuit OR calculates the logical sum of the discharge circuit operation command RS acquired from the cell control unit 101 and the processing signal SPS acquired from the signal processing unit 110. The OR circuit OR supplies the calculated OR to the power supply switch SW2. The power supply switch SW2 switches between a conduction state and a cutoff state based on the value of the logical sum supplied from the logical sum circuit OR. For example, when the calculation result supplied from the OR circuit OR is positive (that is, when at least one of the discharge circuit operation command RS and the processing signal SPS is supplied), the power supply switch SW2 is supplied. Becomes conductive. For example, when the calculation result supplied from the OR circuit OR indicates a negative value (that is, when both the discharge circuit operation command RS and the processing signal SPS are not supplied), the power supply switch SW2 is in a cut-off state.

  With the configuration described above, when the cell control unit 101 outputs the discharge circuit operation command RS and the power supply switch SW2 is turned on, the Zener diode D1 is turned on, and the voltage Vs is held at a certain voltage. Therefore, the signal processing unit 110 supplies the processing signal SPS to the second input terminal of the OR circuit OR. Thereby, even if the cell control unit 101 does not continue to output the discharge circuit operation command RS, the power supply switch SW2 performs signal processing until the voltage Vc decreases so that the voltage Vs cannot be kept constant. The conduction state can be maintained by the processing signal SPS supplied from the unit 110. Therefore, the cell 100d can use the cell control unit 101 to change the increase or decrease of the voltage Vc of the capacitor 105 for switching the power supply switch SW2.

  Further, the cell control unit 101 may stop the operation of the discharge circuit 102 when the voltage Vc of the capacitor 105 detected by the voltage detection unit 104 is lower than the voltage at which the second power feeding circuit 108d operates. . Specifically, when the voltage Vs of the second power feeding circuit 108d is lower than the voltage Vss2, which is the lower limit voltage of the circuit operating voltage of the discharge circuit driving unit 109, the cell control unit 101 outputs a negative signal Supply to sum circuit OR. The OR circuit OR to which the negative signal is supplied switches the power supply switch SW2 to the cutoff state. As a result, the second power supply circuit 108d stops supplying power to the discharge circuit driving unit 109. The discharge circuit driving unit 109 from which the supply of power is stopped stops the supply of the switch control signal SS. The discharge switch SW1 from which the supply of the switch control signal SS from the discharge circuit driving unit 109 has been stopped enters a cutoff state. When the discharge switch SW1 is cut off, the operation of the discharge circuit 102 is stopped.

  In the configuration of the second power feeding circuit 108d described above, the semiconductor switch Q1 may be used as the discharge switch SW1 included in the discharge circuit 102. FIG. 8 is a diagram illustrating another example of the circuit configuration of the discharge circuit 102.

  In the discharge circuit 102b shown in FIG. 8, a semiconductor switch Q1 is used as the discharge switch SW1. The semiconductor switch Q1 is a self-extinguishing type switching element such as a GTO (Gate Turn-Off Thyristor), an IGBT (Insulated Gate Bipolar Transistor), or an IEGT (Injection Enhanced Gate Transistor). This semiconductor switch Q1 has a high breakdown voltage.

  The semiconductor switch Q1 is maintained in the cutoff state before the switch control signal SS is output from the discharge circuit driving unit 109. When the switch control signal SS is output from the discharge circuit driving unit 109 to the gate of the semiconductor switch Q1, the semiconductor switch Q1 becomes conductive.

  As described above, in the power conversion device 10 of the fourth embodiment, in the discharge circuit 102, the voltage Vc of the capacitor 105 detected by the cell control unit 101 is lower than the voltage at which the second power feeding circuit 108 operates. If it stops working. Thereby, even if the voltage Vc of the capacitor 105 is lower than the lower limit voltage at which the first power supply circuit 103 operates, the cell control unit 101 can stop the operation of the discharge circuit 102. When abnormality due to an accident or the like is recovered during the discharging operation of the capacitor 105, the operation of the cell 100 can be restarted at an early stage.

  In addition, although the cell of 1st Embodiment, 2nd Embodiment, 3rd Embodiment, and 4th Embodiment mentioned above demonstrated the structure of the half-bridge type chopper cell, It may be a configuration.

  According to at least one embodiment described above, the power conversion apparatus includes a plurality of cells 100 connected in series with each other, and each cell 100 controls a capacitor 105 and charge / discharge of the capacitor 105. A first switching element 107a and a switching element 107b that perform a switching operation and a first power that supplies power for driving the switching element 107a and the switching element 107b to the switching element 107a and the switching element 107b using the power stored in the capacitor 105. Power supply circuit 103, discharge circuit 102 for discharging capacitor 105, discharge circuit drive unit 109 for driving discharge circuit 102, discharge circuit drive unit 109, and discharge circuit 102 using the electric power stored in capacitor 105 And power to drive A lower power supply voltage at which the second power supply circuit 108 can operate is lower than a lower voltage at which the first power supply circuit 103 can operate, so that the capacitor included in the cell The time for discharging the stored charge can be shortened. In addition, the power converter can sufficiently discharge the electric charge stored in the capacitor included in the cell, and can ensure the safety of an operator who performs maintenance or inspection after an accident.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Power converter, 11 ... Central control part, 12 ... Positive side arm, 13 ... Negative side arm, 100, 100d ... Cell, 101 ... Cell control part, 102, 102a, 102b ... Discharge circuit, 103 ... 1st Feed circuit 104 ... Voltage detection unit 105 ... Capacitor 106 ... Switching element drive unit 107a, 107b ... Switching element 108 ... Second feed circuit 109 ... Discharge circuit drive unit ES ... Converter stop command, RS ... discharge circuit operation command, SS ... switch control signal, SW1 ... discharge switch, SW2 ... feed switch, SPS ... processing signal, SW3 ... self-holding switch, transformer ... TR

Claims (11)

Comprising a plurality of cells connected in series with each other,
A capacitor,
A semiconductor switch that performs a switching operation for controlling charging and discharging of the capacitor;
A first power supply circuit that supplies power for driving the semiconductor switch to the semiconductor switch using the power stored in the capacitor;
A discharge circuit for discharging the capacitor;
A discharge circuit driver for driving the discharge circuit;
A second power supply circuit that supplies power for driving the discharge circuit drive unit using the power stored in the capacitor;
A cell controller that outputs and operates a discharge circuit operation command to the second power supply circuit;
With
When the second power feeding circuit acquires the discharge circuit operation command from the cell control unit, the second power feeding circuit starts supplying power to the discharge circuit driving unit ,
The discharge circuit driving unit outputs a signal for latching a conduction state of the discharge circuit while the voltage is supplied from the second power feeding circuit .
The lower limit voltage at which the second feeding circuit can operate is lower than the lower limit voltage at which the first feeding circuit can operate,
Power conversion device. The power converter according to claim 1. The above-mentioned cell outputs the information which shows the time change of the voltage of the above-mentioned capacitor with which the cell is provided with respect to the central control part which controls a plurality of the above-mentioned cells. The discharge circuit is:
Even if the voltage of the capacitor is lower than the voltage at which the semiconductor switch can operate, it operates with the power supplied by the second power feeding circuit.
The power conversion device according to claim 1. The discharge circuit is:
When the voltage of the capacitor is lower than a predetermined voltage, the capacitor is operated by the power supplied by the second power feeding circuit.
The power conversion device according to claim 2. The discharge circuit is:
When the ratio of the amount of decrease in the voltage of the capacitor with respect to time exceeds a predetermined ratio, the capacitor is operated by the power supplied by the second power feeding circuit.
The power conversion device according to claim 2. The discharge circuit is:
Operates when the user performs an operation to operate the discharge circuit,
The power converter device of Claim 1 or Claim 2. The cell outputs a signal indicating an operation state of the discharge circuit to the central control unit after the power supply operation of the second power supply circuit included in the cell,
The power conversion device according to claim 2. A controller for supplying a discharge stop signal, which is a signal for stopping the discharge circuit, to the discharge circuit;
The discharge circuit stops operation based on a discharge stop signal supplied from the control unit,
The power conversion device according to claim 1. The discharge circuit stops operating when a voltage of the capacitor is lower than a voltage at which the second power feeding circuit operates;
The power conversion device according to claim 1. The discharge circuit includes a switch and a resistor connected in series with the switch.
The power conversion device according to claim 1. The switch is one of a semiconductor switch and a mechanical switch.
The power conversion device according to claim 10.

Images